1. Field of the Invention
The present invention relates to wireless IC devices and, more particularly, to a wireless IC device for use in a Radio Frequency Identification (RFID) system.
2. Description of the Related Art
In recent years, as information management systems for products, RFID systems have been used in which transmission of predetermined information is performed in a non-contact manner between a reader/writer which generates an induction field and an RFID tag (hereinafter also referred to as a wireless IC device) attached to a product. The RFID tag includes a wireless IC chip which stores predetermined information and processes a predetermined radio signal and an antenna (radiator) arranged to transmit/receive a high-frequency signal, and is attached to various management target products (or packages of these products).
Japanese Unexamined Patent Application Publication No. 2007-272264 discloses this type of RFID tag obtained by forming a loop antenna on an insulating film, disposing a wireless IC chip on a portion of the loop antenna, and wrapping the insulating film around a dielectric member.
Products to which such RFID tags are attached have various shapes. For example, a gas cylinder has a curved surface, and it is required that an RFID tag can also be attached to the curved surface. When the RFID tag disclosed in Japanese Unexamined Patent Application Publication No. 2007-272264 includes a dielectric member made of a material such as silicon, the RFID tag can be attached to a curved surface. However, if an RFID tag is attached to a curved surface using only the flexibility of a material, stress concentration may occur between a dielectric member and a loop antenna when the dielectric member is bent. As a result, the loop antenna may be detached from the dielectric member, or a crack may be produced at the dielectric member. Alternatively, the loop antenna may be distorted, a communication characteristic may be changed, and communication reliability may be reduced.